Manufacture of artificial thread



Patented July 13, 1937 UNITED srarss mesne assignments, to E. 1. du Pontde Nemours & Company, Wilmington, Del, a corporation of Delaware NoDrawing. Application February 6, 1933, Serial 3 Claims.

This invention relates to the manufacture of artificial thread. Moreparticularly, it relates to the manufacture of artificial thread formedof an organic derivative of cellulose, such as cellulose acetate, havingproperties which render it suitable for many purposes for which theartificial threads produced prior to this invention could not beemployed.

According to the principles of this invention, there is provided anartificial thread formed of, for example, cellulose acetate, which ischaracterized by. a relatively high dry tenacity, for example, of amagnitude of 1.50 grams per denier or more and a dry elongation of atleast such as ormore. Because of these properties, the threadconstituting one phase of the instant invention is capable of moreextensive use than the ordinary artificial thread formed of celluloseacetate and having a dry elongation at the breaking point not exceeding25%. For example, the thread produced in accordance with the instantinvention is admirably suitable for application involving a subsequentstretching, the high elongation permitting the securing, afterstretching by the various known methods, of fibers which are strong andstill possess a capacity for elongation. Consequently, the thread isparticularly useful in the manufacture of woven articles. Likewise, thisthread can be subjected to a very high degree of twisting and stillpossess, after the twisting operation, a normal elongation of from 18%to 20%. Also, even though the thread has a high elongation at thebreaking point, it is nevertheless adapted to the usual operations ofknitting and weaving. Moreover, the thread is particularly suitable forthe production of fabrics with crepe effects.

The thread previously described may be produced in accordance with themethod hereinafter described and constitutes another phase of theinstant invention. In accordance with the principles of the method, aspinning solution, preferably a cellulose acetate solution of suitableconcentration, is spun through dies in an evaporative atmosphere, as iswell known in the art.

The cellulose acetate solution, which is utilized in the instantinvention, is characterized by a viscosity which does not exceed 100 c.g. s. units at the spinning nozzle. In the preferred embodiment of theinvention, the desired and proper viscosity of the spinning solution issecured by heating a solution of suitable concentration prior to theextrusion thereof. Obviously, in this exemplification, a preheatedsolution is spun.

In Great Britain February 17,

(c1. Iii-54) During the spinning operation, the filaments are onlysubjected to a stretching not exceeding the ratio 2. This ratio of thestretching is defined as the ratio of the length of the finished threadto the length of the thread .resulting from the evaporation withoutstretching of a filament of collodion, assuming that the collodionfilament contracts in the same manner in the three dimensions.Mathematically the stretching ratio can be represented by the followingformulae:

S. R. (stretching ratio) wherein L equals the length of the finishedfilament and L equals the length of the filament resulting from theevaporation of the collodion filament without stretching gig/. 2

wherein V" equals the volume of the collodion which is extruded throughthe spinneret hole, 1 the radius of the spinneret hole, C the percentageconcentration, D the density of the collodion and D the density of thefinished filament.

The evaporative atmosphere in which the solution is spun is maintainedat an appropriate temperature, such as 85 C., and contains a relativelysmall quantity or percentage of solvent vapors. In other words, it maybe described as a dilute evaporative atmosphere.

The elongation properties of the threads produced according to thisinvention are not obtained at the expense of the qualities ofresistance, when dry, with respect to those fibers manufactured underthe normal conditions of dry spinning. On the contrary, generally, thefibers produced according 'tothis invention have higher resistances tobreaking, while their elastic resistances are also better.

A remarkable, unexpected, and indeed surprising feature of the instantinvention is that collodions of such viscosities as contemplated by theinstant invention can be spun and produce threads having the qualitiesof resistance and elongation previously referred to.

In order to more clearly explain the instant invention, there ishereafter set forth an illustrative example. It is to be understood thatthis specific example merely illustrates a specific embodiment of theinvention which has given satisfactory results but that the invention isnot restricted thereto.

ErampleA collodion containing 22.7% of cellulose acetate and 77.3% of asolvent consisttil ing of 85 parts .per volume of acetone and 15 partsper volume of ethyl alcohol is heated to a temperature of 67 C. Underthese conditions, the collodion has a viscosity of c. g. s. units(ascertained by the method of the ball in a sealed tube) The solution isthen extruded under pressure in an evaporative medium through a diecontaining 18 orifices of 0.06 m n. in diameter and the filaments arecollected at the outlet of the spinning cell in the form of a 100 denierthread. The elementary or constituent filaments thereof obviously are100/ 18:55

denier.

The stretching ratio as defined above is 1.75.

The conditions of temperature in the cell and of the circulation of theair for the evaporation of the solvent may be those which are generallyused. Preferably, the cell is heated to a temperature of (3., 3500liters per hour of air are passed therethrough and the spinning carriedout at the rate of meters per minute.

The thread obtained has an average elongation of 34% and resistance ortenacity of 1.58 grams per denier for a hygrometrical state of 47 C. anda temperature of 21 C. The corresponding wet elongation and tenacitiesare 48% and 0.82 gram per denier.

If desired, the spinning solution may contain any modifying agent, suchas coloring agents, fillers and low luster-inducing agents, such aspigments, etc. It is to be understood that the above-mentionedproperties may be secured Without the addition of any plastieizer,although the latter may also be used just as in the case of ordinarycellulose acetate thread.

'Since it is obvious that various modifications may be made in thespecific details above described, the invention is not restrictedthereto 7 except as defined in the appended claims.

I claim:

1. In amethod of preparing artificial thread having an elongation in thedry state of at least 30%, the steps of spinning a cellulose acetatespinning solution having a viscosity not exceed-' ing 100 c. g. s. unitsand stretching the filaments or threads during the spinning operation-tosuch a degree that the stretching ratio does not exceed 2.

2. In a method of preparing artificial thread having an elongation inthe dry state of at least 30%, the steps of spinning a preheatedcellulose acetate spinning solution having a viscosity not exceeding 100c. g. 5. units and stretching the filaments or threads during thespinning operation to such a degree that the stretching ratio does notexceed 2.

3. In'a method of preparing artificial thread having an elongation inthe dry state of at least 30%, the steps Which comprise spinning acellulose acetate solution having a viscosity of 70 c. g. s. units andcontaining 22.7% of cellulose acetate and 77.3% of a solvent consistingof 85 parts per volume of acetone and 15 parts per volume of ethylalcohol and stretching the filaments or threads during the spinningoperation to such a degree that the stretching ratio does not exceed 2.

GUILLAUME LARDY.

